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[Qemu-devel] [Bug 965867] Re: 9p virtual file system on qemu slow
From: |
max |
Subject: |
[Qemu-devel] [Bug 965867] Re: 9p virtual file system on qemu slow |
Date: |
Thu, 26 Apr 2012 20:35:00 -0000 |
Hi Mohan,
this parameter provide significant improvement in big file access/write:
--------------------------------------------------------------------------------------------
VirtFS on /srv/shared type 9p (rw,trans=virtio,version=9p2000.L,msize=262144)
$ dd if=/dev/zero of=test count=100000 bs=16384
100000+0 records in
100000+0 records out
1638400000 bytes (1.6 GB) copied, 36.3589 s, 45.1 MB/s
l$ dd if=/dev/zero of=test count=100000
100000+0 records in
100000+0 records out
51200000 bytes (51 MB) copied, 25.6597 s, 2.0 MB/s
$ dd if=/dev/zero of=test count=1024 bs=262144
1024+0 records in
1024+0 records out
268435456 bytes (268 MB) copied, 3.41936 s, 78.5 MB/s
Speed of copy for large file ~45MB/s (read and write from the same disk).
---------------------------------------------------------------------------------------------
But Host:
time ls -lahs bam.unsorted/
many files:
real 0m0.053s
user 0m0.004s
sys 0m0.036s
VM:
real 0m4.449s
user 0m0.012s
sys 0m0.136s
--------------------------------------------------------
So we have delays on the first file access.
Is it possible to resolve this issue?
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https://bugs.launchpad.net/bugs/965867
Title:
9p virtual file system on qemu slow
Status in QEMU:
New
Status in “qemu-kvm” package in Ubuntu:
Confirmed
Bug description:
Hi,
The 9p virtual file system is slow. Several examples below:
---------------------------------------------------------
Host for the first time:
$ time ls bam.unsorted/
...........................
real 0m0.084s
user 0m0.000s
sys 0m0.028s
--------------------------------------------------
Host second and following:
real 0m0.009s
user 0m0.000s
sys 0m0.008s
------------------------------------------------------
VM for the first time:
$ time ls bam.unsorted/
................................
real 0m23.141s
user 0m0.064s
sys 0m2.156s
------------------------------------------------------
VM for the second time
real 0m3.643s
user 0m0.024s
sys 0m0.424s
----------------------------------------------------
Copy on host:
$ time cp 5173T.root.bak test.tmp
real 0m30.346s
user 0m0.004s
sys 0m5.324s
$ ls -lahs test.tmp
2.7G -rw------- 1 oneadmin cloud 2.7G Mar 26 21:47 test.tmp
---------------------------------------------------
$ copy on VM for the same file
time cp 5173T.root.bak test.tmp
real 5m46.978s
user 0m0.352s
sys 1m38.962s
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